This invention relates to bicomponent poly(trimethylene terephthalate) fibers and processes for the manufacture thereof.
Poly(trimethylene terephthalate) (also referred to as xe2x80x9c3GTxe2x80x9d or xe2x80x9cPTTxe2x80x9d)has recently received much attention as a polymer for use in textiles, flooring, packaging and other end uses. Textile and flooring fibers have excellent physical and chemical properties.
It is known that bicomponent fibers wherein the two components have differing degrees of orientation, as indicated by differing intrinsic viscosities, possess desirable crimp contraction properties which lead to increased value in use for said fibers.
U.S. Pat. Nos. 3,454,460 and 3,671,379 disclose bicomponent polyester textile fibers. Neither reference discloses bicomponent fibers, such as sheath-core or side-by-side fibers, wherein each of the two components comprises the same polymer, e.g. poly(trimethylene terephthalate), differing in physical properties.
WO 01/53573 A1 discloses a spinning process for the production of side-by-side or eccentric sheath-core bicomponent fibers, the two components comprising poly(ethylene terephthalate) and poly(trimethylene terephthalate), respectively. Due to the poly(ethylene terephthalate) fibers and fabrics made from them have a harsher hand than poly(trimethylene terephthalate) monocomponent fibers and fabrics. In addition, due to the poly(ethylene terephthalate) these fibers and their fabrics require high-pressure dyeing.
U.S. Pat. Nos. 4,454,196 and 4,410,473, which are incorporated herein by reference, describe a polyester multifilament yarn consisting essentially of filament groups (I) and (II). Filament group (I) is composed of polyester selected from the group poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly(tetramethylene terephthalate), and/or a blend and/or copolymer comprising at least two members selected from these polyesters. Filament group (II) is composed of a substrate composed of (a) a polyester selected from the group poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly(tetramethylene terephthalate), and/or a blend and/or copolymer comprising at least two members selected from these polyesters, and (b) 0.4 to 8 weight % of at least one polymer selected from the group consisting of styrene type polymers, methacrylate type polymers and acrylate type polymers. The filaments can be extruded from different spinnerets, but are preferably extruded from the same spinneret. It is preferred that the filaments be blended and then interlaced so as to intermingle them, and then subjected to drawing or draw-texturing. The Examples show preparation of filaments of type (II) from poly(ethylene terephthalate) and polymethylmethacrylate (Example 1) and polystyrene (Example 3), and poly(tetramethylene terephthalate) and polyethylacrylate (Example 4). Poly(trimethylene terephthalate) was not used in the examples. These disclosures of multifilament yams do not include a disclosure of multicomponent fibers.
JP 11-189925, describes the manufacture of sheath-core fibers comprising poly(trimethylene terephthalate) as the sheath component and a polymer blend comprising 0.1 to 10 weight %, based on the total weight of the fiber, polystyrene-based polymer as the core component. According to this application, processes to suppress molecular orientation using added low softening point polymers such as polystyrene did not work. (Reference is made to JP 56-091013 and other patent applications.) It states that the low melting point polymer present on the surface layer sometimes causes melt fusion when subjected to a treatment such as false-twisting (also known as xe2x80x9ctexturingxe2x80x9d). Other problems mentioned included cloudiness, dye irregularities, blend irregularities and yam breakage. According to this application, the core contains polystyrene and the sheath does not. Example 1 describes preparation of a fiber with a sheath of poly(trimethylene terephthalate) and a core of a blend of polystyrene and poly(trimethylene terephthalate), with a total of 4.5% of polystyrene by weight of the fiber.
JP 2002-56918A discloses sheath-core or side-by-side bicomponent fibers wherein one side (A) comprises at least 85 mole % poly(trimethylene terephthalate) and the other side comprises (B) at least 85 mole % poly(trimethylene terephthalate) copolymerized with 0.05-0.20 mole % of a trifunctional comonomer; or the other side comprises (C) at least 85 mole % poly(trimethylene terephthalate) not copolymerized with a trifunctional comonomer wherein the inherent viscosity of (C) is 0.15 to 0.30 less than that of (A). It is disclosed that the bicomponent fibers obtained were pressure dyed at 130xc2x0 C.
It is desired to prepare fibers which have excellent stretch, a soft hand and excellent dye uptake, and which can be spun at high-speeds and dyed under atmospheric pressure.
It is also desired to increase productivity in the manufacture of side-by-side or eccentric sheath core poly(trimethylene terephthalate) bicomponent fibers by using higher speed spinning process, without deterioration of the filament and yarn properties.
The invention is directed to a side-by-side or eccentric sheath-core bicomponent fiber wherein each component comprises poly(trimethylene terephthalate) differing in intrinsic viscosity (IV) by about 0.03 to about 0.5 dl/g and wherein at least one of the components comprises styrene polymer dispersed throughout the poly(trimethylene terephthalate).
The invention is also directed to a process for preparing poly(trimethylene terephthalate) side-by-side or eccentric sheath-core bicomponent fibers comprising (a) providing two different poly(trimethylene terephthalate)s differing in intrinsic viscosity (IV) by about 0.03 to about 0.5 dl/g, at least one of which contains styrene polymer, by weight of the polymers, and (b) spinning the poly(trimethylene terephthalate)s to form side-by-side or eccentric sheath-core bicomponent fibers wherein at least one of the component comprises the styrene polymer dispersed throughout the poly(trimethylene terephthalate). Preferably the bicomponent fibers are in the form of a partially oriented multifilament yarn.
The invention is further directed to a process for preparing poly(trimethylene terephthalate) bicomponent self-crimping yarn comprising poly(trimethylene terephthalate) bicomponent filaments, comprising (a) preparing the partially oriented poly(trimethylene terephthalate) multifilament yarn, (b) winding the partially oriented yam on a package, (c) unwinding the yarn from the package, (d) drawing the bicomponent filament yarn to form a drawn yarn, (e) annealing the drawn yarn, and (f) winding the yarn onto a package. In one preferred embodiment, the process comprises drawing, annealing and cutting the fibers into staple fibers.
In addition, the invention is directed to a process for preparing fully drawn yam comprising crimped poly(trimethylene terephthalate) bicomponent fibers, comprising the steps of:
(a) providing two different poly(trimethylene terephthalate)s differing in intrinsic viscosity (IV) by about 0.03 to about 0.5 dl/g, wherein at least one of the poly(trimethylene terephthalate)s comprises styrene polymer;
(b) melt-spinning the poly(trimethylene terephthalate)s from a spinneret to form at least one bicomponent fiber having either a side-by-side or eccentric sheath-core cross-section;
(c) passing the fiber through a quench zone below the spinneret;
(d) drawing the fiber, preferably at a temperature of about 50 to about 170xc2x0 C. and preferably at a draw ratio of about 1.4 to about 4.5;
(e) heat-treating the drawn fiber, preferably at about 110 to about 170xc2x0 C.;
(f) optionally interlacing the filaments; and
(g) winding-up the filaments.
Further, the invention is directed to a process for preparing poly(trimethylene terephthalate) self-crimped bicomponent staple fiber comprising:
(a) providing two different poly(trimethylene terephthalate)s differing in intrinsic viscosity by about 0.03 to about 0.5 dl/g, wherein at least one of them comprises styrene polymer;
(b) melt-spinning the compositions through a spinneret to form at least one bicomponent fiber having either a side-by-side or eccentric sheath-core cross-section;
(c) passing the fiber through a quench zone below the spinneret;
(d) optionally winding the fibers or placing them in a can;
(e) drawing the fiber;
(f) heat-treating the drawn fiber; and
(g) cutting the fibers into about 0.5 to about 6 inches staple fiber.
Preferably the poly(trimethylene terephthalate)s differ in IV by at least about 0.10 dl/g, and preferably up to about 0.3 dl/g.
Preferably the styrene polymer is selected from the group consisting of polystyrene, alkyl or aryl substituted polystyrenes and styrene multicomponent polymers, more preferably polystyrenes.
The styrene polymer is preferably present in a component in an amount of at least about 0.1%, more preferably at least about 0.5, and preferably up to about 10 weight %, more preferably up to about 5 weight %, and most preferably up to about 2 weight %, by weight of the polymers in the component.
In a preferred embodiment, the styrene polymer is present in each of the components.
In another preferred embodiment the styrene polymer is present in only one of the components. In one preferred embodiment the styrene polymer is in the component with the higher IV poly(trimethylene terephthalate). In a second preferred embodiment the styrene polymer is in the component with the lower IV poly(trimethylene terephthalate).
Preferably each component comprises at least about 95% of poly(trimethylene terephthalate), by weight of the polymer in the component.
Preferably each of the poly(trimethylene terephthalate)s contains at least 95 mole % trimethylene terephthalate repeat units.
Advantages of the invention over fibers and fabrics made from poly(trimethylene terephthalate) and poly(ethylene terephthalate) include softer hand, higher dye-uptake, and the ability to dye under atmospheric pressure.
When the styrene polymer is in the higher IV poly(trimethylene terephthalate) (including when it is in both poly(trimethylene terephthalates), the fibers of this invention can be prepared using higher spinning speeds, higher drawing speeds and higher draw ratios than other poly(trimethylene terephthalate) bicomponent fibers.
When styrene polymer is added to the lower IV poly(trimethylene terephthalate) or to the lower IV poly(trimethylene terephthalate) in greater amount than the higher IV poly(trimethylene terephthalate), the differences between the molecular orientation of the poly(trimethylene terephthalate)s will increase, and crimp contraction and stretch increases.
By varying the amount of polystyrene in each side (or section), or only adding it in one side (or section), it is possible to further control the crimp level and stretch.